An integrated circuit, for example, included in a wireless communication base station, controls a process that includes mapping a first downlink control channel to control channel element(s) (CCE(s)) in a first search space comprised of a first plurality of CCEs, the first downlink control channel including resource assignment information, which indicates a resource allocated to a terminal in a component carrier n (CCn) out of one or more component carrier(s) (CC(s)), and mapping a second downlink control channel to CCE(s) in a second search space comprised of a second plurality of CCE(s), the second downlink control channel including resource assignment information, which indicates a resource allocated to the terminal in a component carrier n+1 (CCn+1) out of the CC(s), the first plurality of CCEs and the second plurality of CCEs are consecutive. The process also includes transmitting the first and the second downlink control channels to the terminal.